Move codex module under session (#18249)

## Summary
- rename the core codex module root to session/mod.rs without using
#[path]
- move the codex module directory and tests under core/src/session
- remove session/mod.rs reexports so call sites use explicit child
module paths

## Testing
- cargo test -p codex-core --lib
- cargo check -p codex-core --tests
- just fmt
- just fix -p codex-core
- git diff --check

codex-rs/core/src/tools/handlers/agent_jobs.rs

@@ -1,10 +1,10 @@
 use crate::agent::exceeds_thread_spawn_depth_limit;
 use crate::agent::next_thread_spawn_depth;
 use crate::agent::status::is_final;
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::config::Config;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/apply_patch.rs

@@ -7,9 +7,9 @@ use std::sync::Arc;
 use crate::apply_patch;
 use crate::apply_patch::InternalApplyPatchInvocation;
 use crate::apply_patch::convert_apply_patch_to_protocol;
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::ApplyPatchToolOutput;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::SharedTurnDiffTracker;

codex-rs/core/src/tools/handlers/dynamic.rs

@@ -1,6 +1,6 @@
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/js_repl.rs

@@ -54,8 +54,8 @@ fn build_js_repl_exec_output(
 }
 
 async fn emit_js_repl_exec_begin(
-    session: &crate::codex::Session,
-    turn: &crate::codex::TurnContext,
+    session: &crate::session::session::Session,
+    turn: &crate::session::turn_context::TurnContext,
     call_id: &str,
 ) {
     let emitter = ToolEmitter::shell(
@@ -69,8 +69,8 @@ async fn emit_js_repl_exec_begin(
 }
 
 async fn emit_js_repl_exec_end(
-    session: &crate::codex::Session,
-    turn: &crate::codex::TurnContext,
+    session: &crate::session::session::Session,
+    turn: &crate::session::turn_context::TurnContext,
     call_id: &str,
     output: &str,
     error: Option<&str>,

codex-rs/core/src/tools/handlers/js_repl_tests.rs

@@ -1,7 +1,7 @@
 use std::time::Duration;
 
 use super::parse_freeform_args;
-use crate::codex::make_session_and_context_with_rx;
+use crate::session::tests::make_session_and_context_with_rx;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::ExecCommandSource;
 use pretty_assertions::assert_eq;

codex-rs/core/src/tools/handlers/mcp_resource.rs

@@ -17,9 +17,9 @@ use serde::Serialize;
 use serde::de::DeserializeOwned;
 use serde_json::Value;
 
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/mod.rs

@@ -28,9 +28,9 @@ use serde::Deserialize;
 use serde_json::Value;
 use std::path::Path;
 
-use crate::codex::Session;
 use crate::function_tool::FunctionCallError;
 use crate::sandboxing::SandboxPermissions;
+use crate::session::session::Session;
 pub(crate) use crate::tools::code_mode::CodeModeExecuteHandler;
 pub(crate) use crate::tools::code_mode::CodeModeWaitHandler;
 pub use apply_patch::ApplyPatchHandler;

codex-rs/core/src/tools/handlers/multi_agents.rs

@@ -7,9 +7,9 @@
 
 use crate::agent::AgentStatus;
 use crate::agent::exceeds_thread_spawn_depth_limit;
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/multi_agents_common.rs

@@ -1,8 +1,8 @@
 use crate::agent::AgentStatus;
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::config::Config;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/multi_agents_tests.rs

@@ -1,10 +1,10 @@
 use super::*;
 use crate::CodexThread;
 use crate::ThreadManager;
-use crate::codex::make_session_and_context;
 use crate::config::AgentRoleConfig;
 use crate::config::DEFAULT_AGENT_MAX_DEPTH;
 use crate::function_tool::FunctionCallError;
+use crate::session::tests::make_session_and_context;
 use crate::session_prefix::format_subagent_notification_message;
 use crate::state::TaskKind;
 use crate::tasks::SessionTask;
@@ -60,7 +60,7 @@ use tokio::time::timeout;
 use tokio_util::sync::CancellationToken;
 
 fn invocation(
-    session: Arc<crate::codex::Session>,
+    session: Arc<crate::session::session::Session>,
     turn: Arc<TurnContext>,
     tool_name: &str,
     payload: ToolPayload,

codex-rs/core/src/tools/handlers/plan.rs

@@ -1,6 +1,6 @@
-use crate::codex::Session;
-use crate::codex::TurnContext;
 use crate::function_tool::FunctionCallError;
+use crate::session::session::Session;
+use crate::session::turn_context::TurnContext;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;

codex-rs/core/src/tools/handlers/request_user_input_tests.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::codex::make_session_and_context;
+use crate::session::tests::make_session_and_context;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolPayload;
 use crate::turn_diff_tracker::TurnDiffTracker;

codex-rs/core/src/tools/handlers/shell.rs

@@ -4,13 +4,13 @@ use codex_protocol::models::ShellToolCallParams;
 use serde_json::Value as JsonValue;
 use std::sync::Arc;
 
-use crate::codex::TurnContext;
 use crate::exec::ExecCapturePolicy;
 use crate::exec::ExecParams;
 use crate::exec_env::create_env;
 use crate::exec_policy::ExecApprovalRequest;
 use crate::function_tool::FunctionCallError;
 use crate::maybe_emit_implicit_skill_invocation;
+use crate::session::turn_context::TurnContext;
 use crate::shell::Shell;
 use crate::tools::context::FunctionToolOutput;
 use crate::tools::context::ToolInvocation;
@@ -80,7 +80,7 @@ struct RunExecLikeArgs {
     hook_command: String,
     additional_permissions: Option<PermissionProfile>,
     prefix_rule: Option<Vec<String>>,
-    session: Arc<crate::codex::Session>,
+    session: Arc<crate::session::session::Session>,
     turn: Arc<TurnContext>,
     tracker: crate::tools::context::SharedTurnDiffTracker,
     call_id: String,
@@ -140,7 +140,7 @@ impl ShellCommandHandler {
 
     fn to_exec_params(
         params: &ShellCommandToolCallParams,
-        session: &crate::codex::Session,
+        session: &crate::session::session::Session,
         turn_context: &TurnContext,
         thread_id: ThreadId,
         allow_login_shell: bool,

codex-rs/core/src/tools/handlers/shell_tests.rs

@@ -6,9 +6,9 @@ use core_test_support::PathBufExt;
 use core_test_support::test_path_buf;
 use pretty_assertions::assert_eq;
 
-use crate::codex::make_session_and_context;
 use crate::exec_env::create_env;
 use crate::sandboxing::SandboxPermissions;
+use crate::session::tests::make_session_and_context;
 use crate::shell::Shell;
 use crate::shell::ShellType;
 use crate::shell_snapshot::ShellSnapshot;

codex-rs/core/src/tools/handlers/tool_suggest.rs

@@ -155,8 +155,8 @@ impl ToolHandler for ToolSuggestHandler {
 }
 
 async fn verify_tool_suggestion_completed(
-    session: &crate::codex::Session,
-    turn: &crate::codex::TurnContext,
+    session: &crate::session::session::Session,
+    turn: &crate::session::turn_context::TurnContext,
     tool: &DiscoverableTool,
     auth: Option<&codex_login::CodexAuth>,
 ) -> bool {
@@ -194,8 +194,8 @@ async fn verify_tool_suggestion_completed(
 }
 
 async fn refresh_missing_suggested_connectors(
-    session: &crate::codex::Session,
-    turn: &crate::codex::TurnContext,
+    session: &crate::session::session::Session,
+    turn: &crate::session::turn_context::TurnContext,
     auth: Option<&codex_login::CodexAuth>,
     expected_connector_ids: &[String],
     tool_id: &str,

codex-rs/core/src/tools/handlers/unified_exec_tests.rs

@@ -13,7 +13,7 @@ use std::fs;
 use std::sync::Arc;
 use tempfile::tempdir;
 
-use crate::codex::make_session_and_context;
+use crate::session::tests::make_session_and_context;
 use crate::tools::context::ExecCommandToolOutput;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolPayload;